I want to share my experience with migration to latest DSM. I know the thread title clearly says 5.2 to 6.0.2 but i hope it is not a problem if i share my 5.2 to 6.1.2 experience.
I run HP ProLiant Gen8 (G1610) box with 3xHDD, it was DSM 5.2 baremetal.
Downloaded Jun's loader 1.02b (kept original Extra.lzma ramdisk). Modified grub.cfg with SN and mac1+mac2 which i used on DSM 5.2 and of course corrected VID and PID. I never reflashed the NIC, so the MAC addresses are true to factory HW setup. Just to be sure i changed the manual IP to automatic IP from DHCP in DSM - no idead if it is neccessary, but it couldn't do any harm right?
Turned off the server, swapped the USB stick, checked correct setup in BIOS (AHCI, network boot off,...), restart. Choosed first option in Jun's loader and back to pc.
NAS went up on network just fine, choose migrate, provided the DSM 6.1.2-15132 .pat file. It showed error13 "file corrupted". After intial WTF moment i found the file was downloaded incomplete - MD5 checksum didn't matched and file was little bit smaller than it should be (saw some posts about this error earlier here where the guy was sure to have correct vid/pid so maybe this might be the issue). After repeated download the file was OK. I must say that synology server was really slow and the speed was very unstable, guess that's why the .pat file was incomplete at the first time. Anyway, this time the migration went fine. After restart it took some time till the NAS come up in the network and some more time till i was able log in (login screen told me to wait as the database is rebuilding, whatever it means).
Windows pcs couldn't acces mapped drives over SMB after migration. Reseting password (seting the same) did the trick and pcs connected to mapped drives just fine. I don't have mac or linux pc so i couldn't test if it's only windows/SMB problem.
I need to run more tests to be sure everything is OK, but so far everything seems to be running nicely. However it is less then 24hours since i migrated so i am little caucious about making happy statement. Noticed there is already update 1, but i'll wait a little while till i do it.
Last but not least i have to THANK very much to the devs, admins, mods and all users for hard work on loaders, tutorials and comments.